Non-bouncing magnetic contactor



March 18, 1958 -T. H. LEE

NON-BOUNCING MAGNETIC CONTACTOR 3 Sheets-Sheet 1 Filed Dec. 29, 1954 BYHarris/flake March 18, 1958 1'. H. LEE 2,827,527

NON-BOUNCING MAGNETIC CONTACTOR Filed Dec. 29. 1954 3 Sheets-Sheet 2 C"1 KISS POS/T/ON 5 m V DROP our pos/r/o/v K/SS POS/T/ON DROP our POS/T/QN"W K/SS POSITION A v V OPEN POSITION KISS v POS/T/ON OPEN POS/ T/ON IN VEN TOR.

Xtwrny T. H. LEE

NON-:BOUNCING MAGNETIC .CONTACTOR March 18, 1958 3 Sheets-Sheet 3 FiledDec. 29, 1954 INVENTOR. BY 7%0765 1G6 United States Patent NON-BOUNCINGMAGNETIC CONTACTOR Thomas Henry Lee, Schenectady, N. Y., assignor toGeneral Electric Company, a corporation of New York Application December29, 1954, Serial No. 478,251

13 Claims. (Cl. 200-87) My invention relates to magnetically actuatedapparatus for opening and closing electrical contacts in response toelectrical currents.

More particularly, my invention relates to magnetic contactors havingfairly heavy magnetic armatures which upon deenergization of theelectromagnet drop away from the magnetic core and open a pair ofelectrical contacts by this drop-out movement.

In such magnetic contactors, backstops are normally provided forlimiting the drop-out movement of the armature to an air-gap distancebetween the armature and pole faces of the electromagnet determinedprimarily by the magnetic force characteristic desired as well as by thecontact separation desired. One of the long standing problems in thedesign of such contactors has been the tendency of heavy armatures torebound after striking the backstop thereby causing the movableelectrical contact connected thereto sometimes lightly to restrike thestationary contact. The electrical current passing through thesemomentarily lightly engaging surfaces of the electrical contacts may besufiicient to weld the contacts together or cause arcing which burns orotherwise damages the electrical contacts. Accordingly, an importantobject of the invention is to provide a contactor construction whichinherently clamps out and reduces the amplitude of rebound of themagnetic armature after striking the backstop.

Another object of the invention is to provide an armature reboundreducing mechanism which can be easily incorporated in existing magneticcontactors without major change in the design of the contactors.

In general, in accord with the invention, a magnetic contactor isconstructed and arranged so that either the armature or its backstop hasan additional degree of freedom of movement upon impact and the force oftheir impact is transmitted to and absorbed by an inertia member or massduring movement of the armature or backstop along this additional pathor degree of freedom. The additional degree of freedom of movement maybe linear movement or rotational movement but should be along adifferently directed path from that taken by the magnetic armatureduring its drop-out movement toward the backstop. It has been found thatthe provision of this additional degree of differently directed freedomof movement in the armature or in the backstop in itself tends to reducerebound of the armature and that the presence of an inertia mass orfriction restricted member within this second degree of freedomfunctions to reduce to an unusual extent the initial rebound of thearmature by immediate and almost total absorption of the energy ofimpact between the armature and its backstop.

The invention may be easily embodied in contactors having armatureswhich move along arcuate as well as linear paths. The inertia mass orfriction restricted member may be constrained to move along a pathcorresponding to the second degree of freedom by respective connectionto. either the armature or the backstop and this movement may either belinear or areuate.

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The novel features believed characteristic of the invention are setforth in the appended claims. The invention itself, however, togetherwith further objects and advantages thereof can be easily understood byreferring to the following description taken in connection with theaccompanying drawings in which:

Figure 1 is a side view partly in section of the magnet and armatureportion of a contactor embodying the invention;

Figure 2 is a front view in outline of the contactor of Figure 1;

Figure 3 is a pair of comparative charts of tests illustrating thedifference in magnitude of rebound in a contactor such as illustrated inFigure 1 before and after the incorporation of the rebound reducingmechanism of the invention; 7

Figure 4 is a side view partly in section of another magnetic contactorembodying the invention;

Figure 5 is a perspective view of a friction restricted resilientmounting means for the armature of the contactor of rigure 4; and

Figure 6 is a pair of charts similar to Figure 2 of tests taken inconnection with a contactor such as illustrated by Figure 4.

Referring to Figures 1 and 2 the invention is shown in connection with amagnetic contactor 9 of the type having an armature assembly 10pivotally mounted at one end to provide an arcuate drop-out path,designated by arrow A, between the other end 12 of armature 11 and apole face 13 of a U-shaped magnetic core 14 of the eiectrornagnet 15.Contactor 9 has a supporting backplate 16 upon which magnetic core 14 ismounted by suitable supporting brackets 17. Armature 11 is U- shaped andhas flat end faces 18 and 19 confronting and constructed to engage polefaces 13 and 20,-respectively, of magnetic core 14 when in magneticallyattracted position. Resilient pole-shading clips 21 and 22 fit withinsuitable recesses 23 and 24, respectively, in the pole faces 13 and 20of magnetic core 14.

A bifurcated bracket 25 of armature assembly 16 carries armature 11 andis fastened to a pivotally mounted shaft 26. Spaced brackets 27 securedto supporting backplate 16 serve pivotally to support shaft 26 withinsuitable bearings 23. As best seen in Figure 2, shaft 26 carries amovable contact 29 which engages stationary contacts 30 when the shaft26 is rotated by the attraction of armature assembly 11 toward magneticcore 14.

In accord with the invention, a backstop member 31 is arranged to arrestthe movement of armature assembly 11 by engagement during drop out witha stop pin 32 carried by the armature mounting bracket 25. Stop pin 32preferably comprises an inner cylindrical metal rod 33 surrounded by acylinder 34 of tough non-metallic shock absorbent material.

The backstop assembly including backstop member 31 is resilientlymounted on supporting backplate 16 by virtue of interconnected metalstrips 35 and 36 and spring washer fastening means 37 and 38. Morespecifically, backstop member 31 has a downwardly extending portion 39which receives the impact of stop pin 32 and a laterally extendingportion 40 which is fastened by bolt 41 to the metal strip 35. Strip 35,in turn, is spot welded at its other end to mounting strip or bracket 36which is resiliently mounted on backplate 16 by screws 37 and 38 underthe resilient tension of spring washers 42 and 43.

A coil 44 for energizing electromagnet 15 is mounted on metal strip 35between a downwardly extending flange 45 of backstop member 31 and anupwardly extending flange 46 of supporting bracket 36 which flanges bearagainst opposite sides of coil frame 47.

In accord with the invention the flat under-surface of coil carryingmetal strip 35 bears against and slides upon the upper flat surface ofmagnet core 14 in frictional engagement therewith. The entireresiliently mounted backstop assembly com-prising backstop member 31 andconnecting strips 35 and 36 has a degree of freedom of movement along apath or direction B generally corresponding to the plane of the uppersurface 48 of core 14. The movement of this backstop assembly withinthis degree of freedom is impeded, however, by the inertia of the systemincluding the mass of coil 44 carried thereon as well as by the frictiongenerated between the undersurface of strip 35 and the upper surface 48of core 14. It will be appreciated that relative movement between thesesurfaces is possible since the core structure is securely supported onpanel 16 whereas bracket 36 is resiliently mounted on panel 16 andcapable of having some displacement therefrom. As shown in Figure l, anonmagnetic shim 49 may be inserted between these relatively movingsurfaces to take up any play and to increase the friction, if necessary.When armature assembly drops out of contact with magnetic core 14 as aresult of the deenergization of coil 44, stop pin 32 strikes backstopportion 39 and the force of impact produces a slight linear movement ofthe backstop assembly as determined by the inertia, friction andresilient mounting of the backstop assembly. Substantially the entirekinetic energy in the moving armature assembly 10 is transmitted to andimmediately absorbed by the differently directed and friction restrictedmovement of the backstop assembly such that the armature assembly comesto rest with relatively little rebound as compared to similar magneticcontactors where the backstop is rigidly supported or has a freedom ofmovement only in the same direction or along the same path as thearmature assembly was traveling when striking the backstop.

The remarkable improvement in reduction of rebound in a contactorembodying the invention is illustrated by the curves of Figure 3. CurveC is a copy of an actual plot taken by a position recorder of themovement of the armature of a magnetic contactor such as is illustratedin Figure l but with the backstop assembly rigidly mounted by omittingspring washers 42 and 43 and securely tightening bolts 37 and 38. CurveD is a similar plot with the backstop assembly resiliently mounted inaccord with the invention described above. With the rigidly mountedbackstop arrangement plotted by curve C the armature typically reboundedto a small distance S corresponding to a small distance between thecontacts 29 and 30 carried by shaft 26. Any additional shock orvibration of the contactor might increase the amplitude of armaturerebound such thatthe contacts would lightly retouch or kiss causingwelding or other damage to the contacts. With the differently directedfreedom of movement of the resiliently mounted backstop assembly of theinvention, the armature assembly 10, as shown by curve D, upon strikingthe backstop 32 almost immediately returns with practically no reboundto its drop-out position such that the distance S between the contacts29 and 30 always remains great enough that simultaneous vibration cannotcause the contacts to retouch.

Referring now to Figure 4, the invention is shown in connection with amagnetically actuated contactor 50 in which the armature assembly 51 isconstructed and arranged to move along a linear drop-out path ratherthan along an arcuate path as in contactor 9 of Figure 1. Contactor 50comprises a supporting backplate 52 having a pair of spaced horizontallyextending arms 53 (only one shown) which carry the general magnetic coreassembly including a coil frame and armature guide assembly 54. A metalmounting bracket 55 inserted through a central aperture in coil 56 ofelectromagnet 57 is fastened to backplate 52. by bolts 53 and functionsto carry the laminations of magnetic core'59 as wellas to providemounting means for one end of L-shaped backstop strip member 60 securedthereto by bolts 61. The other end of backstop member 60 is supported onbackplate 52 within a suitable slot 62 therein.

Armature assembly 51 comprises an armature 63 of U-shaped sectioncarrying pole shading clips 64, 65 and mounted on a plunger or guidemember 66. Plunger 66 is also of U-shaped section having a pair ofvertically extending arms 67 and 68 connected by horizontal cross piece69 inserted within channels 70, 71 formed in the upraised legs of thearmature laminations 63. Guide arms 67 and 68 of plunger 66' areslidable within suitable recesses or channels 72 vertically extendingalong the sides of coil frame 54.. The upper ends of guide arms 67 and68 are connected by bolts 73 to an insulating cross bar 74. Cross bar 74carries the contact assembly 75 including a pair of interconnectedcontacts '76, 77 which bridge a pair of stationary contacts 78 and 79,respectively, when brought into engagement therewith by the verticalmotion of armature assembly 51.

In accord with the invention, armature assembly 51 is constructed tostrike its backstop member 60 along an axis 80 offset fromthe region ofsupport of armature 63, and the armature 63 is provided with anadditional freedom of movement, namely a freedom to move slightly in arotational or arcuate path relative to the line or axis of contact 80between the armature and its backstop 60. More specifically, backstopmember 60 is bent upward slightly along its horizontal leg 81 in orderthat the vertically descending armature 63 will strike the apex of thebent portion 81 of backstop 60 along the apex line 80. This is incontrast with prior constructions where leg 81 was formed and supportedparallel to the bottom surface of armature 63 in order that both fiatsurfaces might make plane-to-plane large area contact previously thoughtdesirable. As a result of the-upwardly bent condition of backstop leg81, armature 63 tends to rock about its initial impact axis 80. Thisrocking motion of armature 63 is permitted by virtue of a predeterminedlooseness of fit or play between the armature 63 and the cross piece 69of guide member 66 on which it is mounted. The mechanism for mountingarmature 63 on plunger 66 preferably also includes means'for resilientlyreturning the armature to the position wherein its pole faces areparallel to those of magnetic core 59 and also for frictionally impedingthe rocking motion of armature 63 after impact with backstop 60.

The details of this friction restricted mounting between the contactoperating mechanism and the armature assembly are shown in Figure 5.Cross piece 69 of plunger 66 has a slight central spherical depression82. A flat, slightly resilient thin metal plate 83 rests on cross piece69 with its opposite ends beneath inturned projections 84, 85 ofarmature 63. Flexible plate 83 also has a central spherical depression86 resting within depression. 82 of cross piece 69 but of slightlygreater depth such that the bottom of depression 86 applies a downwardpressure resiliently biasing the'remaining laterally ex tending portions69" of cross piece 69 in spaced relation both to the coextendingportions of plate 83 as well as in spaced relation to the channels 70and 71 in armature 63. An insulating shim 87 may be inserted beneathcross piece 69 on the upper fiat surface of armature 63 inorder to takeup any extra play between the surfaces, although this shim may not benecessary. If used, shim 87 is slightly spaced from the side portions 69of cross piece 69 in order to permit a slight rocking motion of armature63 before either shimj87 or plate 83 comes into contact with the sideportions of cross piece 69. During such rocking motion the depressedportion 82 of cross piece 69 acts as a bearingsurface upon which thedepressed portion 86 of plate 83 is journalled. The sliding or rockingmotionof the bottomsurface of spherical depression 86of plate83 on theupper spherical surface of depres- R2 of cross piece 69 and the uppercontacting area of shim 87 immediately beneath this surface introducesadditional friction impeding the rocking motion of armature 63. It willbe appreciated that the rocking motion of armature 63 on the bearingsurface formed by the depression 82 in plunger cross piece 69 resultsfrom the transmittal of the rocking motion of the armature 63 about theline of contact 80 between the armatur 63 and the bent backstop 60.After the shock of impact and consequent rocking and rebound of armature63 has passed, the armature returns to an at rest position shown inFigure 4 as a result of the resilient nature of plate 83 and thesymmetry of the spherical depression 86 and 82.

The typical reduction in rebound resulting from the use of the inventionin a contactor such as shown in Figure 4 is illustrated by the curves ofFigure 6. In Figure 6 curve E is a plot taken by a position recorder ofthe position of movable contact 76, 77 relative to stationary contact78, 79 during drop out of a contactor identical with that shown inFigure 4 with the exception that horizontal backstop leg 81 wasperfectly flat and parallel to the undersurface of armature 63-such thatthere is no rocking motion of armature 63 induced. Curve F of Figure 6is a similar plot of the same contactor during drop out with thehorizontal backstop leg 81 bent upward to provide the off-center initialstriking axis 80 in accord with the invention. The improvement inreduction of rebound is apparent from a comparison of these curves.

Although I have disclosed specific embodiments of the invention, manymodifications can be made and I intend by the appended claims to coverall such modifications as fall within the true spirit and scope of theinvention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

l. A magnetically actuated device comprising supporting means, abackstop assembly on said supporting means, a magnetic armature assemblyon said supporting means arranged to strike said backstop assemblyduring dropout movement along a first general path, one of saidassemblies being supported for movement after impact between saidassemblies along a dilferently directed path from said armature assemblydrop-out path, a substantially rigid member supported on said supportingmeans remote from the region of backstop engagement between saidassemblies, and a friction restricted member frictionally engaging saidrigid member and connected for movement after said impact by and withthe assembly movable along said differently directed path thereby toreduce rebound of said armature assembly after striking said backstopassembly.

2. The magnetically actuated device of claim 1 wherein the armatureassembly is supported for movement along a difierently directed pathfrom its drop-out path after striking the backstop assembly and thefriction restricted member is connected for movement after impactbetween said assemblies by and with the armature assembly.

3. The magnetically actuated device of claim 1 wherein the backstopassembly is supported for movement along a difierently directed pathfrom said armature assembly drop-out path after being struck by saidarmature assembly, and the friction restricted member is connected formovement after said impact by and with the backstop assembly.

4. The magnetically actuated device of claim 1 wherein the armatureassembly strikes said backstop assembly by drop-out movement along anarcuate path, and one of said assemblies is supported for movement alonga linearly directed path after impact between said assemblies.

5. The magnetically actuated device of claim 1 wherein the armatureassembly strikes the backstop assembly by drop-out movement along alinear path, and one of said assemblies is supported for movement alongan arcuate path after impact between said assemblies.

6. Magnetically actuated apparatus for operating electrical contactscomprising, supporting means, a backstop assembly on said supportingmeans, a magnetic armature assembly on said supporting means connectedto move one of said contacts and constructed to strike said backstopassembly during drop-out movement along a first general path, one ofsaid assemblies being supported for movement after impact between saidassemblies along a differently directed path from said armature assemblydrop-out path, a substantially rigid member supported on said supportingmeans remote from the area of impact between said assemblies, a movablemember frictionally engaging said rigid member and connected formovement after impact between said assemblies by and with the assemblymovable along said differently directed path, and resilient meansconnected to said latter assembly for returning said magnetic armatureassembly to substantially its initial striking position.

7. Magnetically actuated apparatus for operating electrical contacts,comprising a backstop assembly and a magnetic armature assemblyconnected to move one of said contacts and arranged to strike saidbackstop assembly during drop-out movement along a first general path,resilient mounting means for said backstop assembly and frictioninducing means contacting said backstop assembly in an area remote fromthe area of impact between said assemblies for frictionally reducingmovement of said backstop assembly on its resilient mounting after beingstruck by said armature assembly.

8. The magnetically actuated apparatus of claim 7 wherein said frictioninducing means supports and guides said backstop for movement along adifferently directed path from said armature assembly drop-out path.

9. Magnetically actuated apparatus for operating electrical contacts,comprising an electromagnet having a magnetic core and a magneticarmature assembly connected to move one of said contacts, a resilientlymounted backstop assembly located in the drop-out path of said magneticarmature assembly, said backstop assembly being resiliently movable onits mounting in frictional engagement with a surface of the magneticcore of said electromagnet in an area removed from the area of impactbetween said assemblies.

10. The magnetically actuated apparatus of claim 9 wherein a coil forsaid electromagnet is carried by said backstop assembly.

ll. A magnetically actuated apparatus for operating electrical contactscomprising, a supporting plate, an electromagnet having a stationaryportion rigidly mounted on said plate and having a movable magneticarmature assembly connected to operate said electrical contacts, abackstop assembly having one end resiliently mounted on said supportingplate and having a portion remote from said one end in the path ofdrop-out movement of said armature assembly, and means carried by saidbackstop assembly for frictionally engaging said electromagnetstationary portion during movement of said backstop assembly on itsresilient mounting after impact with said magnetic armature assembly.

12. Magnetically actuated apparatus for operating electrical contactscomprising, a supporting plate, an electromagnet having a magnetic coreassembly rigidly mounted on said supporting plate and having a movablearmature assembly for operating said contacts, means supported by saidcore assembly for guiding said armature assembly to move in a lineardrop-out direction relative to said core assembly, means resilientlymounting said armature assembly for limited rotational movement about asmall area bearing surface of said guiding means, and a backstop memberlocated to be struck by said armature assembly during its drop-outmovement in an area remote from and eccentric to said bearing surfacearea thereafter to translate the linear motion of said armature assemblyinto a rotational motion, thereby to reduce rebound of said armatureassembly.

a seam-e27 13. Magnetically. actuated apparatus for operating electricalcontacts comprising a supporting plate, anelectromagnet having amagneticcore assembly rigidly mounted on said supporting plate and a movablearmature, a contact operating mechanism connected between one of saidelectrical contacts and said armature, said operating mechanism beingsupported on said core assembly for sliding movement along a generallylinear drop-out path, means resiliently mounting. said armature forfrictionally restricted rotation on a spherical bearing surface of saidoperating mechanism and a backstop member connected between saidsupporting plate and said core assembly, said backstop member havingatconfiguration and location to be struck by said armature in an arearemote and eccentric from saidspherical bearing surface of saidresilient mounting means. thereby to translate linear dropout motionofsaidjarmature into a frictionally restricted rotational motion.. J

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990,512 I Barnum n- Apr. 25, 1911 1,331,290 Stratton Feb. 17, 19201,334,144 Eaton Mar. 16, 1920 1,764,819 Anderson June 17, 1930 1,948,688Ad-am 5; Feb. 20, 1934 2,235,391 Williams et al.- -'Mar; 18, 19412,240,589 Wagar' May 6, 1941 2,361,808 Ayers -a Oct. 31, 1944 2,412,304Staley Dec. 10, 1946- 2,584,707 Jarvis et al, -a Feb. 5, 1952'

